1. Field of the Invention
The invention relates to a helicopter, and more particularly to a helicopter having a downwash flow control function.
2. Description of Related Art
Spraying of chemicals or fertilizers using a helicopter has been put into practice in an agricultural field or the like. In such spraying operation, the helicopter generally maintains low speed almost hovering at the height of having high influence of ground effect so as to adhere the chemicals in mist even to the backside of leaves of crops to be sprayed, effectively utilizing the downwash generated by the rotation of a rotor of the helicopter.
FIG. 6 shows a downwash flow generated by the rotor rotation of the helicopter. It has been known that, as shown in FIG. 6, the downwash D flows downward at high speed along fuselage side surfaces 110 of a helicopter 100 and separates at a fuselage lower surface 120 to produce irregular air current C. Therefore, when spraying nozzles are disposed at the lower surface 120, the irregular air current C causes lots of chemicals to adhere to the lower surface 120, and the adhered chemicals fall as droplets or a part of chemicals is sometimes not sprayed, resulting in lower spraying efficiency. In order to avoid this, nozzles 200 are often disposed apart from a fuselage 101 of the helicopter 100 as shown in FIG. 7.
Recently, various kinds of technologies have been proposed for controlling such downwash flow. For instance, such a technology is disclosed that, by providing a flow control device (a forming member, a drift plate, a cover, etc.) at the upper part of a helicopter fuselage, a rescuer or a worker positioned under the fuselage can avoid being directly exposed to a strong downwash (see, for example, JP-Tokukaihei-7-47998A).
When spraying chemicals using a helicopter, it is effective to diffuse the chemicals by the downwash generated by the rotor rotation of the helicopter. However, the technology described in above JP-Tokukaihei-7-47998A would lead to a problem that it cannot effectively utilize the downwash.
If adopted the technology that uses nozzles disposed apart from the helicopter fuselage (see FIG. 7), supporting members having nozzles mounted thereon need to be long in order to avoid adhesion of chemicals to the lower part of the fuselage due to the downwash, resulting in weight increase of the helicopter. Accordingly, it has long been desired to develop a new technology for reducing the weight of a helicopter and simultaneously for improving spraying efficiency.
When spraying chemicals or the like, the helicopter keeps low speed almost hovering flight at the height of having high influence of ground effect as described before, and therefore the generation of irregular air current under the fuselage due to the downwash leads to a problem of impairing the stability of the body during flight, and reducing controllability.